1. Field of the Invention
This invention relates to an antiglare film which is applied on a surface of a window or a display etc. In particular, this invention relates to an antiglare film which is used on a surface of a display such as liquid crystal display (LCD), CRT (Cathode Ray Tube) display, organic electroluminescent display (ELD), plasma display (PDP), surface conduction electron-emitter display (SED) and field emission display (FED) etc.
2. Description of the Related Art
In the field of displays such as LCD, CRT display, ELD and PDP, an arrangement of an antiglare film which has a concave-convex structure on the surface thereof on the display is known as a means for preventing a degradation of visibility caused by reflection of external light on the display surface during viewing.
The following techniques, for example, are known for producing such antiglare films:                a method of forming a concave-convex structure on an antiglare film surface by emboss processing;        a method of coating a coating liquid obtained by admixing particles to a binder matrix forming material and dispersing the particles in the binder matrix, thereby forming a concave-convex structure on an antiglare film surface.        
In such antiglare film having on the surface thereof a concave-convex structure formed by the above-described methods, external light falling on the antiglare film is scattered by the concave-convex structure of the surface. As a result, the image of external light becomes smudgy so that the degradation of visibility caused by the reflection of external light on the display surface is prevented.
In the antiglare film in which convexities and concavities have been formed on the surface by emboss processing, surface convexities and concavities can be completely controlled. As a result, reproducibility is good. However, the problem is that when defects or foreign matters are present on the emboss roll, the defects spaced by a roll pitch appear continuously on the film.
On the other hand, the antiglare film using a binder matrix and particles can be produced by using fewer operations than the antiglare film employing the emboss processing. As a result, this type of antiglare film can be manufactured at a low cost. Accordingly, antiglare films of a variety of forms in which particles are dispersed in a binder matrix are known (Japanese Patent Application Publication (JP-A-6-18706) No. 6-18706).
Various techniques have been disclosed with respect to antiglare films using binder matrix and particles. For example, the following methods for producing antiglare films using a binder matrix and particles have been disclosed:                a method using a binder matrix resin, spherical particles, and particles of irregular shape (JP-A-2003-260748);        a method using a binder matrix resin and particles of a plurality of different diameters (JP-A-2004-004777);        a method of using a film having surface convexities and concavities in which the cross-sectional area of convexities is specified (JP-A-2003-004903).        
In addition, the following methods have also been disclosed:                a method of using internal scattering in combination with external scattering and setting an internal haze of an antiglare film to 1-15% and a surface haze to 7-30% (JP-A-11-305010);        a method of using a binder resin and particles with a size of 0.5-5 μm and setting the difference in refractive index between the resin and the particles to 0.02-0.2 (JP-A-11-326608);        a method of using a binder resin and particles with a size of 1-5 μm and setting the difference in refractive index between the resin and the particles to 0.05-0.15, and a method in which the properties of the solvent used and the surface roughness are set within the predetermined ranges (JP-A-2000-338310);        a method of using a binder resin and a plurality of particles and setting the difference in refractive index between the resin and the particles to 0.03-0.2 (JP-A-2000-180611);        a method of setting a surface haze to 3 or more and setting the difference between a haze value in the normal direction and a haze value in the direction at ±60° to 4 or less with the object of reducing the variations in hue and the decrease in contrast occurring when the viewing angle changes (JP-A-11-160505).        
As described above, various techniques for various purposes have been disclosed. The required properties and performances for an antiglare film which is applied on a frontal surface of a display device depend on the type of the display. In other words, the most desirable antiglare film for a display device differs depending on the display's resolution and intended use etc. Therefore, a wide variety of antiglare films to meet various applications are wanted.
Recently, an antiglare film having (1) a sufficient antiglare property, which makes an image derived from external light smudgy when it falls in the surface of the antiglare layer's side, and showing (2) weaker ‘white-blurring’, which is observed as whitening phenomenon of the antiglare film when an illumination such as fluorescent light is reflected on the surface of the antiglare layer's side, tends to be preferred. Especially in the case where the antiglare film is applied on the surface of an LCD as TV, the antiglare film is required to have a high level of antiglare property causing a low level of white-blurring phenomenon if any.
The present invention provides an antiglare film having a high level of antiglare property and at the same time causing no significant white-blurring.